1. Field of the Invention
The present invention relates to a fuel injection apparatus used in a marine engine such as an outboard motor for sailing on the sea.
2. Description of Conventional Art
A description will be given of a conventional fuel injection apparatus for the marine engine with reference to FIG. 3.
Reference symbol T denotes a fuel tank in which fuel is stored, reference symbol V denotes a vapor separator within which a fixed fuel liquid surface X—X is formed, and reference symbol D denotes a fuel distribution pipe provided with fuel injection valves J injecting and supplying the fuel into intake pipes K of the engine.
Further, the vapor separator V is structured as follows.
Reference numeral 20 denotes a cup-shaped casing. An upper opening of the casing 20 is closed by a cover 21.
Reference symbol F denotes a fixed liquid surface control mechanism which forms and holds the fixed fuel liquid surface X—X within the vapor separator V. The fixed liquid surface control mechanism F is constituted by a valve seat 23 which is connected to an inflow passage 22 formed in the cover 21 and is open to the inside of the vapor separator V, a float valve 24 which opens and closes the valve seat 23, and a float 26 which is rotatably supported to an axis 25, swings in correspondence to a liquid surface height formed within the vapor separator V, and controls so as to open and close the valve seat 23 via the float valve 24.
Further, a high pressure electric pump HP is arranged within the vapor separator V, and this electric pump HP is constituted by a direct current motor portion DM and a pump portion P. The pump P is structured such that an impeller 31 provided with a plurality of vane grooves in a peripheral edge portion is rotatably arranged within a pump chamber recess portion 30 formed between a first casing 28 and a second casing 29 which are arranged below a cylindrical pump housing 27.
Further, a pump inflow passage 32 and a pump outflow passage 33 are arranged so as to be open to the pump chamber recess portion 30, and the upstream side of the pump inflow passage 32 is open downward and is open within the vapor separator V. On the other hand, the downstream side of the pump outflow passage 33 is open within the pump housing 27 above the first casing 28. (In the following description, the upstream and downstream are described with respect to a flowing direction of the fuel.)
The direct current motor portion DM is constituted by an armature 35 attached to a motor axis 34 both ends of which are rotatably pivoted, a commutator 36 which is attached to the motor axis 34 and is connected to the armature 35, a brush 37 which is in slidable contact with the commutator 36, and a semicylindrical permanent magnet 38 which is arranged inside the pump housing 27 so as to face to the armature 35, and the direct current motor portion DM is arranged inside the pump housing 27.
Further, an upper opening of the pump housing 27 is closed by a pump cover 39, a pump discharge passage 40 is formed in the pump cover 39, the upstream side of the pump discharge passage 40 is communicated with the inside of the pump housing 27 in which the direct current motor portion DM is received, and the downstream side thereof is open toward the outside.
The high pressure electric pump HP provided with the direct current motor portion DM and the pump portion P is shown, for example, in Japanese Patent Publication No. 63-63756.
Further, the electric pump HP is arranged within the vapor separator V, the pump discharge passage 40 is connected to a discharge passage 41 provided in the cover 21, and the pump inflow passage 32 is arranged so as to open below the fixed liquid surface X—X within the vapor separator V via a suction side filter 42.
Further, the fuel injection apparatus of the marine engine is formed in the following manner.
The fuel tank T and the vapor separator V are communicated via a low pressure fuel pump LP. The low pressure fuel pump LP and the fuel tank T are communicated by a low pressure fuel suction passage 43, and the low pressure fuel pump LP and the inflow passage 22 of the vapor separator V are communicated by a low pressure fuel discharge passage 44.
Further, a fuel distribution pipe D and the high pressure electric pump HP are communicated via the high pressure fuel filter HF. The high pressure fuel filter HF and the discharge passage 41 of the cover 21 are communicated by a first high pressure discharge passage 45, and the high pressure fuel pump HF and the fuel distribution pipe D are communicated by a second high pressure fuel discharge passage 46.
Further, a pressure regulator. R is attached to the fuel distribution pipe D, and a return fuel pipe 47 of the pressure regulator R is communicated with the inside of the vapor separator V.
In accordance with the fuel injection apparatus for the marine engine structured in the manner mentioned above, the fuel within the fuel tank T is sucked into the low pressure fuel pump LP via the low pressure fuel suction passage 43, and the fuel the pressure of which is increased to low pressure (for example, 0.3 kg/cm2) by the fuel pump LP is supplied within the vapor separator V via the low pressure fuel discharge passage 44, the inflow passage 22 and the valve seat 23.
In the vapor separator V, the low pressure fuel is supplied, whereby the fuel is stored within the vapor separator V, and the fixed fuel liquid surface X—X is formed and held within the vapor separator V by a fixed liquid surface control mechanism F.
On the other hand, the direct current motor portion DH of the high pressure electric pump HP is rotated and driven, whereby the impeller 31 is also rotated within the pump chamber recess portion 30 by the motor axis 34. In accordance with this structure, the fuel within the vapor separator V is sucked into the pump chamber recess portion 30 via the intake side filter 42 and the pump inflow passage 32, and the high pressure fuel the pressure of which is increased to high pressure (for example, 3 kg/cm2) within the pump chamber recess portion 30 reaches the pump discharge passage 40 via the pump outflow passage 33, and a motor space portion A formed between the direct current motor portion DM and a pump casing 27 surrounding the direct current motor portion DM.
Further, the high pressure fuel in the pump discharge passage 40 is supplied to the high pressure fuel filter HP via the cover discharge passage 41 and the first high pressure fuel discharge passage 45, the high pressure fuel from which foreign materials are removed by the high pressure fuel filter HP is supplied to the fuel distribution pipe D via the second high pressure fuel discharge passage 46, and this fuel is electrically supplied within the intake pipes K via the fuel injection valves J.
On the other hand, when the pressure of the fuel within the fuel distribution pipe D is increased over predetermined pressure, the pressure regulator R releases the return fuel pipe 47, whereby the surplus fuel is again circulated into the vapor separator V via the return fuel pipe 47. Accordingly, it is possible to maintain the fuel having predetermined fuel pressure within the fuel distribution pipe D.
The direct current motor portion DM of the conventional high pressure electric pump HP mentioned above is arranged within the pump housing 27, and the high pressure fuel within the pump housing 27 flowing from the pump portion P toward the pump discharge passage 40 is in contact with the direct current motor portion DM.
That is, the high pressure fuel flows down toward the pump discharge passage 40 while being in contact with the direct current motor portion DM.
This is provided for the purpose of cooling the direct current motor portion DM, lubricating the commutator 36 and the brush 37 and lubricating the motor axis 34 and the bearing portion.
Here, in the case of using the fuel injection apparatus mentioned above as the marine engine, there is a risk that vapor containing sea water and splash of sea water enter into the fuel tank T and the vapor separator V. For example, they possibly enter at a time of connecting the fuel pipe or they possibly enter from an opening portion in an air vent hole of the fuel tank T or the vapor separator V.
Further, when pressure of the fuel (gasoline or fuel mixture of gasoline and engine oil) in which the sea water is mixed as in the case mentioned above is increased by the pump portion P of the high pressure electric pump HP, and the fuel containing the sea water is stirred so as to be brought into contact with the armature 35, the commutator 36 and the brush 37 constituting the direct current motor portion DM, a metal ion such as a calcium, a magnesium or the like contained in the sea water is combined so as to generate a metal soap in some cases.
Further, the metal soap mentioned above is peeled off from the direct current motor portion DM by the high pressure fuel flowing through the periphery thereof, and the metal soap is caught by the high pressure filter HF via the first high pressure fuel discharge passage 45.
In this case, the high pressure fuel filter HF is to be cleaned compulsorily by a driver after a fixed time use, however, if this cleaning is not carried out, there is generated a problem that a flow passage resistance is increased by the high pressure fuel filter HF, and the fuel supply to the fuel distribution pipe D is reduced.
Further, in the case that the cleaning is not carried out for a long time period, there is a risk that a clogging of the high pressure fuel filter HF caused by the metal soap is promoted, and the high pressure fuel filter HF is largely deformed by the high pressure fuel.
Further, in the case that the high pressure electric pump HP is in an unused state for a long time period, an oxide film due to the sea water tends to be generated on an outer peripheral surface of the commutator 36 other than the contact portion of the commutator 36 with a leading end portion of the brush 37, which is not preferable in electric current conduction between the commutator 36 and the brush 37.
Furthermore, an ethanol is often mixed in gasoline fuel in recent years, however, in accordance with this structure, the mixing of the sea water and the gasoline is promoted due to an interposition of an alcohol, and the problem mentioned above is expanded.
Still further, there can be considered a so-called dry motor system in which the direct current motor portion and the pump portion are isolated by a coupling portion, and the fuel the pressure of which is increased by the pump portion is not moved to the direct current motor portion, however, in accordance with this structure, a size of the fuel pump is increased and the number of the parts is largely increased, so that it is not practically preferable.